AMHERST — Squads of police in riot gear mobilized four times Saturday to break up large groups of revelers participating in this year’s Blarney Blowout, each time making arrests as they moved in on groups that assembled in dense crowds.

The confrontations grew violent at times with participants throwing bottles and cans at the police, who in turn sought to single out individuals who they wrestled to the ground, often twisting a limb if the person wasn’t submitting to arrest.

In all, 73 people were arrested on charges ranging from minor alcohol infractions to assault and battery on a police officer. Another 28 were to be summoned to court.

The University of Massachusetts Amherst said students who violated the school’s code of conduct face disciplinary action.

School spokesman Ed Blaguszewski said in a statement that the conduct of those arrested by either town or campus police will be examined by the dean of students. “Sanctions can include suspension or expulsion from the university,” the statement said.

Capt. Christopher Pronovost said that given the amount of alcohol being consumed, allowing the crowds to persist and grow posed a serious threat to public safety due to flying bottles and the outbreak of fights. The first crowd of several thousand young people formed at 10 a.m., the Police Department said. It left the UMass campus and moved north on North Pleasant Street.

Once it arrived at the Puffton Village Apartment complex, it continued to grow, police said. By 11 a.m., vehicles were unable to move through the area. Bottles, cans and snowballs were thrown and police dispersed the crowd.

That scenario was replayed at Brandywine Apartments at 12:15 p.m., where the crowd was estimated at 4,000, and then again just after 1:30 p.m. near downtown at North Pleasant and Fearing streets.

Each time one of the dense crowds was dispersed, the ground where they had gathered was littered with thousands of empty beer cans and bottles. Participants could be seen vomiting and staggering due to drunkenness.

Fire Chief Walter “Tim” Nelson said several revelers were taken to the hospital and a larger number were treated at the scene for lacerations to the limbs and head, some related to falling. At least four police officers sustained injuries, none requiring a trip to the hospital, including a cut to the hand stemming from a thrown object.

Nelson said some participants were treated for having dangerously high levels of alcohol in their systems.

Pronovost characterized the day’s events as “mayhem.”

“This can’t in any way, shape or form be characterized as a party,” he said. “This is destruction of property and assaultive behavior.”

Pronovost said students could be seen fighting with each other. “It gets worse every year. If they need somewhere to go, something should be organized for them,” the captain said.

Amherst police used 20 officers to respond to Blarney Blowout, with other staffing provided by UMass and state police, the department said.

Before Saturday, UMass had warned all students in an email message that misconduct would not be tolerated. It asked them to act safely and respect the property of others. Further, it notified students who had already been disciplined for “alcohol-related misconduct” that bad behavior could bring consequences.

The smell of tear gas hung in the air after each of the confrontations.

Selin Uzumcu, an 18-year-old freshman studying business, was upbeat about the day. “Blarney Blowout 2014 was a blast, even though I got tear-gassed.”

A woman identifying herself as Megan Kenny, a first-year student, said of the event, “There is a lot of booze and a lot of crazy fun.”

A young woman who identified herself as Taylor Beaton, a 19-year-old sophomore studying biology, said the event showed the power of numbers. “UMass thinks they have authority. But when you have 25,000 people, they’re going to do what they want to do.”

She witnessed the police crackdown at Brandywine, saying of it, “There might have been a more peaceful way of doing it.”

Andrew Newcomb of Holyoke, a manager at Brandywine, was picking up trash around the complex after the crowd had moved on. He said he had called the police when the crowd started to gather and was told by the dispatcher that they were already on the way. “If they get drunk in this kind of a crowd, things can get violent,” he said.

Many participants made their way south from Brandywine to the Fearing Street area, as messages flew across social media identifying that part of town as the next gathering spot.

Police said the gathering near the town center was associated with a party around the Pi Kappa Alpha fraternity house at 374 North Pleasant St. When officers moved to clear the area, they were again pelted with “glass bottles, full beer cans, rocks, snowballs,” according to a department release. Items were thrown from the roof, windows and porch of the house, police said, prompting them to respond to occupants inside.

As of 7:30 p.m., the arrest total was 43. Charges included failure to disperse and inciting a riot (18), assault with a dangerous weapon (three) and breaking and entering (one). Other charges were disorderly conduct, liquor law violations and assault and battery on police officers.

Pronovost said he had expected this pattern to recur through the afternoon and evening. With revelers communicating through social media, “a party can swell from 50 to 5,000 in a matter of minutes,” he said.

A senior in the UMass Department of Hospitality and Tourism Management who declined to give his last name said the pattern of cat-and-mouse battles between students and police is part of the game.

Raul Colon, an Amherst resident of the last 32 years, came to collect bottles and cans to redeem after the afternoon confrontation near the intersection of Fearing and North Pleasant Streets.

He said he first saw several thousand people gather at that spot as early as 7 a.m. Describing the scenes that repeated themselves throughout the day, he said, “It looks like a revolution, like in the countries that have revolutions between the students and the government.”